• Journal of Korea Foundry Society
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• v.13 no.6
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• pp.540-546
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• 1993

The effects of fluid flow on the purification of aluminum were studied. As the revolution rate(N) increased, the size of columnar grain decreased gradually. The concentration of solidified crystal was decreased with increasing distance from chill and revolution rate(N). Distribution boundary layer thickness(${\delta}$) was calculated from the solute distribution obtained in solid experimentally and by use of BPS equation. The value of ${\delta}$ changed from about $60{\mu}m$ at N value of 27rpm to about $15{\mu}m$ at N value of 1000rpm. From this result, high purification was obtained by decreasing the diffusion boundary layer under forced convection.

• Bulletin of the Korean Chemical Society
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• v.7 no.3
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• pp.241-245
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• 1986

The vibration-vibration energy exchange of $N_2(v=1)+O_2(v=0){\to}N_2(v=0)+O_2(v=1)$ has been investigated, in particular, at low temperatures. The energy exchange rate constants are calculated by use of the solution of the time-dependent Schrodinger equation with the interaction potential of the colliding molecule as a perturbation term. The predicted rate constants are significantly agree with a experimental values in the range of 295∼$90^{\circ}K$. The consideration of the VV-VT coupling decreases the predicted pure VV energy exchange value by a factor of ∼2. When the collision frequency correction is introduced, the VV-VT rate constant is consistent with the observed value in the liquid phase. The consideration of the population of the rotational energy level increases the VV-VT value significantly.

• Korean Journal of Materials Research
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• v.22 no.4
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• pp.185-189
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• 2012

We report plasma-assisted molecular beam epitaxy of $In_XGa_{1-X}N$ films on c-plane sapphire substrates. Prior to the growth of $In_XGa_{1-X}N$ films, GaN film was grown on the nitride c-plane sapphire substrate by two-dimensional (2D) growth mode. For the growth of GaN, Ga flux of $3.7{\times}10^{-8}$ torr as a beam equivalent pressure (BEP) and a plasma power of 150 W with a nitrogen flow rate of 0.76 sccm were fixed. The growth of 2D GaN growth was confirmed by $in-situ$ reflection high-energy electron diffraction (RHEED) by observing a streaky RHEED pattern with a strong specular spot. InN films showed lower growth rates even with the same growth conditions (same growth temperature, same plasma condition, and same BEP value of III element) than those of GaN films. It was observed that the growth rate of GaN is 1.7 times higher than that of InN, which is probably caused by the higher vapor pressure of In. For the growth of $In_xGa_{1-x}N$ films with different In compositions, total III-element flux (Ga plus In BEPs) was set to $3.7{\times}10^{-8}$ torr, which was the BEP value for the 2D growth of GaN. The In compositions of the $In_xGa_{1-x}N$ films were determined to be 28, 41, 45, and 53% based on the peak position of (0002) reflection in x-ray ${\theta}-2{\theta}$ measurements. The growth of $In_xGa_{1-x}N$ films did not show a streaky RHEED pattern but showed spotty patterns with weak streaky lines. This means that the net sticking coefficients of In and Ga, considered based on the growth rates of GaN and InN, are not the only factor governing the growth mode; another factor such as migration velocity should be considered. The sample with an In composition of 41% showed the lowest full width at half maximum value of 0.20 degree from the x-ray (0002) omega rocking curve measurements and the lowest root mean square roughness value of 0.71 nm.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.46 no.4
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• pp.415-424
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• 2020

In the present study, we have refined gomisin N, which represents activity in the proliferation of dermal papilla cells (HFDPCs) from the fruit of Schisandra chinensis (S. chinensis), and have identified optimal extraction conditions for obtaining extracts with high content of gomisin N. The activity of the extracts and fractions was evaluated, and the results indicated approximately 29% proliferation activity in the group treated with 1 ㎍/mL of n-hexane fraction. Column chromatography was used to assess the active ingredient in the n-hexane fraction, and two compounds, namely gomisin N(1) and schisandrin(2), were isolated and identified. When the HFDPCs proliferation activity was tested for the isolated compounds, gomisin N exhibited ≥ 20% proliferation activity. Thus, via response surface methodology (RSM), the optimum extraction conditions to obtain the maximum level of gomisin N from the fruit of S. chinensis were determined, where ethanol proportion, extraction time, and extraction temperature were used as the independent variables. The results revealed coefficient of determination ≥ 0.95 and p-value ≤ 0.05, which confirmed the fit of the model. The optimum extraction conditions to achieve the maximum content of gomisin N were as follows: ethanol proportion 83.8%, extraction temperature 80 ℃, and extraction time 8.7 h. The content of gomisin N using these conditions was predicted as 378,300 ppm, and a mean value close to the predicted value (376,884 ppm) was obtained while validating the aforementioned conditions.

• Journal of Life Science
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• v.18 no.4
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• pp.467-473
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• 2008

This study was performed to investigate the antioxidant effect of 80% ethanol extracts from Pimpinella brachycarpa in vitro. The extraction yields of 80% ethanol extract was 9.23 g/100 g. The extract was further fractionated subsequently by n-hexane, chloroform, ethylacetate, n-butanol and water. Water fraction showed the highest extraction yield among fractions. Antioxidative activities of different fractions were examined by 1,1-diphenyl-2-picryl hydrazyl (DPPH) radical generation, Rancimat test, thiobarbituric acid (TBA) value, nitrite scavenging activity, inhibition of lipid peroxidation and peroxide value in linoleic acid in comparison with the commercial antioxidant butylated hydroxytoluene (BHT). Antioxidant activities of n-hexane fraction of Pimpinella brachycarpa ethanol extract were the highest among fractions. Furthermore, the antioxidative capacity of the n-hexane fraction was similar to that of BHT.

• Korean Journal of Environmental Agriculture
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• v.14 no.1
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• pp.97-108
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• 1995

Nitrate concentration and ${\delta}^{15}N$ value in the groundwater in Miyakojima Island, Okinawa, were measured during 1992-1993. Water from the shallow and the deep wells at the ten separate sites were sampled. Mineral contents and natural nitrogen isotope abundance(${\delta}^{15}N$) were analyzed using a liquid chromatography and a mass spectrometry (Finnigan MAT 252). Except for waters which were directly influenced by sea water invasion, most of the groundwater showed small variations among their mineral contents and ${\delta}^{15}N$ values. The average nitrate nitrogen concentrations were $1.4{\sim}11.5mgL^{-1}$ and average ${\delta}^{15}N$ values were +4.3${\sim}$+9.7$%_o$. From the nitrate concentration and ${\delta}^{15}N$ value observed, the types of the groundwater could be categorized into four groups, such as high ${\delta}^{15}N$ and high nitrate, high ${\delta}^{15}N$ and medium nitrate, low ${\delta}^{15}N$ and medium nitrate, and low ${\delta}^{15}N$ and low nitrate, reflecting the main source of nitrate contamination, such as animal and domestic waste, animal waste and soil organic matter, soil organic matter and chemical fertilizer, and chemical fertilizer, respectively. It was discussed that the lowest ${\delta}^{15}N$ value was higher than the ${\delta}^{15}N$ value of the chemical fertilizers used in this island(-3.9${\sim}$-1.4$%_o$), then considerable amounts of nitrogen must be lost by ammonium evaporation or denitrification after fertilization.

• 한국초전도학회:학술대회논문집
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• 2008.08a
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• pp.34-34
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• 2008

• Journal of the Korean Mathematical Society
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• v.37 no.6
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• pp.1031-1042
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• 2000

The equations prescribed in Ω⊂R(sup)n are called loaded, if they contain some operations of the traces of desired solution on manifolds (of dimension which is strongly less than n) from closure Ω. These equations result from approximations of nonlinear equations by linear ones, in the problems of optimal control when the control when the control actions depends on a part of independent variables, in investigations of the inverse problems and so on. In present work we study the nonlocal boundary value problems for first-order loaded differential operator equations. Criterion of unique solvability is established. We illustrate the obtained results by examples.

• Bulletin of the Korean Mathematical Society
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• v.53 no.1
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• pp.29-38
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• 2016

For a transcendental entire function f(z) with zero order, the purpose of this article is to study the value distributions of q-difference polynomial $f(qz)-a(f(z))^n$ and $f(q_1z)f(q_2z){\cdots}f(q_mz)-a(f(z))^n$. The property of entire solution of a certain q-difference equation is also considered.

• Journal of the Korean Mathematical Society
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• v.56 no.6
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• pp.1475-1488
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• 2019

In this paper, we firstly define the Ricci mean value along the gradient vector field of the Ricci potential function and show that it is non-negative on a compact Ricci soliton. Furthermore a Ricci soliton is Einstein if and only if its Ricci mean value is vanishing. Finally, we obtain a compact Ricci soliton $(M^n,g)(n{\geq}3)$ is Einstein if its Weyl curvature tensor and the Kulkarni-Nomizu product of Ricci curvature are orthogonal.